Unsaturated polyester coating compositions having controlled resistance to penetration



,faces to a renewed life.

Uite States Patent Ofifice 3,h77,d2t Pa n ed Fe 2 953 3,077,424 UNSATUPATMB PGLYEfilEER .CUA'EENG (IEMPGSL 'iiGNS HAVE-JG GJQNTRQLLEE RESETNNCE T PEIQETRA'HQN Walter E. Maker, La Grange, and Al r: M. Laurlnaitis, tChieago, iii, assignors to Giidden Company, Qieveland, @hio, a corporation of thin No illrawing. Fired Sept. 25, 1956, her. No. 612,072 4 Claims. (tL l. 117 -44-8) As the above title suggests, this invention relates to 109% polymerizable coatings of the unsaturated polyester type, which have been modified in viscosity prop erties to have good hold-out when applied to porous sub strates such as wood, plaster, concrete, etc. The resulting coatings have the desirable property of not sinking into such porous substrates and are thereby retained on the surface of the latter to provide a hard and tough protective layer. The modified coatings also possess excellent adhesion, and by suitable formulation can be adequately ilexible to expand and contract with the substrate without cracking or eparatin". While the invention is based largely on the controlled penetration features described above, an important aspect of the invention is to employ such coatings as the vehicle and subsequent binder for abrasive mineral fillers such as pumice, sand, glass, clay, Carborundum, etc., thereby to impart non-skid properties to the coatin s and adapting them for use as tread surfaces on floors or stairs. The same coatings also provide excellent protective layers on walls such as of corridors which, because of the nature of the traffic through such corridors, are exposed to sliding wear, impact, etc. tending to damage the walls.

Freight cars represent a type of structure which can be benefited greatly by protecting the floor and inner sidewalls with the coatings of the present invention. As is well-known, freight cars such as box cars have a heavy wooden floor and wood-surfaced side walls, wood being used primarily so that crates, machinery, boxes, etc. carried therein can be firmly braced in place by nailing braces of various kinds to either the floor or the side walls. In the course of use, the floors and side walls of box cars become badly roughened and splintered both by the nailing and by the abuse entailed in ordinary loading and unloading operations. Hand trucks, power lift trucks, slcids, pinch-bars, the bumping of crates or machinery against the walls, inching operations wherein crates and machinery are moved bodily over the fioor by use of pinch bars or levers all contribute to the roughening, splintering and other deterioration of the wooden surfaces of the floors and side walls. We have found both to our surprise and that of railroad personnel that our filled polyester coatings can be applied to such abused Wooden surfaces of used box cars to provide renewed surfaces far better adapted than the original surfaces to take such abuse without interfering with the prime requisite of permitting nailing into the renewed floor and/ or wall surfaces. Morewer, because of the abrasive fillers employed in our coatings, the surfaces are skidproof even when wet with rain or snow and give good traction for workmen or powered devices such as lift trucks. The coatings have been found to be very durable when exposed to the normally-abrasive conditions entailed in loading and unloading box cars and eliminate the splintering which previously was the result of nailing or of heavy sliding forces. As a result, it has been found to be commercially practicable to use our coatings to restore badly worn box car floors and wall sur- Since the coatings can be applied rapidly and cured within a days time or faster at atmospheric temperatures of 65 F. or above, worn box cars can be renewed and restored to service within a days time, whereas the same box car would normally be out of service for two to three weeks when the old floor and side walls are removed and replaced with new lumher. The use of our coatings therefore significantly upgra es a worn box car while yet keeping it out of service for a minimum period of time.

Our coatings can, of course, be used for other tread surfaces, as on the wood or concrete floors of warehouses, manufacturing plants, and shops of various sorts where heavy loads combined with sliding or gelling forces tend to cause the floor to deteriorate rapidly. On floor side wall surfaces of other buildings where wear is less of a factor than is cleanliness, as in laundries, bake-shops, dairies, etc., but where toughnessand chemical resistance are important, our coatings can be used to great advantage as protective layers capable of giving long service-life. Accordingly, it is an object of this invention to pro: vide novel coating compositions of the unsaturated poly ester type which have been modified to exhibit good hold-out properties when applied to porous substrates.

Another object is to provide coatings of the above kinds which yield cured layers adapted for tread service and for other kinds of service where nailability, abrasion resistance, chemical resistance and/or smoothness along with skid-proof qualities are desired.

These and other obiects will be apparent from the foregoing and ensuing description of our invention.

The described hold-out qualities (that is, resistance to the tendency for a liquid coating composition to sink into a porous substrate) are imparted to our coatings by incorporating finely-divided solid materials of inorganic nature in quantities sufficient to yield rheological characteristics in the liquid coating analogous to those exhibited by thixotropic materials. In the technical sense of physical chemists, thixotropy is defined (Hackhs Chemical Dictionary) as The property possessed by certain gels of becoming fluid on shaking and coagulating again when left at rest.

Our modified coatings, however, are not true gels, but instead are viscous liquids which exhibit relatively high internal resistance to shearing stresses when the stresses are slowly applied, but which become materially more fluid when shearing forces are applied rapidly.

This type of rheological property is not new, and reference is made to US. Patent No. 2,709,689 where similar rheological properties were developed in emulsion coatings and were found to impart good hold-out properties to the coatings. The eachings of that patent in reference to the rheological properties of the coatings are here incorporated by reference. To the best of our knowledge, however, no one prior to our present invention intentionally developed similar rheological properties in polymerizable coatings of the unsaturated polyester type. While the latter coatings are liquids, they are not emulsions, and instead can be cured in their entirety to a tough resinous mass. In contrast with emulsions they are wholly organic in their essential composition, a the following description will show:

THE UNSATURATED POLYESTER COMPONENT As is now well lmown, a polymerizable unsaturated polyester is prepared by reaction of a polyhydric alcohol with ethylenically unsaturated polycarboxylic acid. It is preferable to employ a dihydric alcohol and a dicarboxylic acid in order to produce a product in which there is a maximum esterification of the acid and alcohol radicals Without excessive viscosity. Ordinarily it is desirable that the unsaturated polyester be polymerizable into an intusible or high melting point resin so that the proportion of unsaturated components should be such that the polyester contains an average of more than one double bond per molecule; for example, there may be an average of eleven or more double bonds in every ten molecules of the polyester.

The polymerizable unsaturated polyester may be produced by reaction of any desired combination of polycarboxylic acid and polyhydric alcohol. For example, an unsaturated dicarboxylic acid such as maleic, fumaric, itaconic, citraconic or mesaconic acid may be reacted with a dihydric alcohol such as any polymethylene glycol in the series from ethylene lycol to decamethylene glycol, propylene glycol, any butylene glycol, any polyethylene glycol in the series from diethylene glycol to nonaethylene glycol, dipropylene glycol, any glycerol monobasic acid monoester (either in the alpha or beta position), such as monoformin or monoacetin, any monoether of glycerol with a monohydric alcohol, such as monomethylin or monoethylin, or any dihydroxy alkane in which the alcohol radicals are primary or secondary or both, in the series from dihydroxy butane to dihydroxy decane.

Each of such unsaturated dicarbcxylic acids contains a polymerizably reactive d -enedioyl group, and a polymerizable unsaturated polyester or alkyd prepared from any one of such acids contains a plurality of such polymerizably reaction A -enedioyl groups. In other words, each of the acids contains a polymerizably reactive A -enoyl group & l l! (1. e., a group having the structure :O-(fi) and such groups are contained in dioyl radicals in the polyester molecule; hence, the dioyl radicals may be defined as A -enedioyl radicals (e.g., butenedioyl or ethenedicarboxylyl radicals).

instead of a single polycarboxylic acid, a mixture or" polycarboxylic acids may be employed, such as a mixture of an unsaturated dicarboxylic acid with a polycarboxylic acid containing more than two acid radicals, such as citric acid. A mixture of polyhydric alcohols may be employed, such as a mixture of dihydric alcohol with a polyhydric alcohol containing more than two hydroxyl groups, such as glycerol.

In the preparation of the polymerizable unsaturated polyester, any of the usual modifiers such as monobasic acids, monohydric alcohols and natural resin acids may be added. The larger the proportions of monobasic acids and monohydric alcohols, the lower is the average number of acid and alcohol residues in the resulting polyester molecules, and the lower is the viscosity of the polyester. On the other hand, the more nearly equal the molecular proportions of dibasic acid and dihydric alcohol the greater is the average number of residues in the resulting polyester molecules, and the greater is the viscosity. The proportions of ingredients used are those proportions that produce a polymerizable polyester of the desired viscosity. Other properties or the polyester, such as solubility in various solvents, also may be varied by selecting various reacting ingredients and varying their proportions. The infusibility, hardness and inertness oi the product obtained by polymerization of the polyester may be increased by varying the initial reacting ingredients to increase the average number of double bonds per molecule of the polymerizable polyester.

The point to which the reaction of the ingredients is carried in the preparation of the polymerizable polyester is simply that point at which the product has the desired properties. The consistency or viscosity of the polyester varies directly with average number of acid and alcohol residues in the molecule. For example, the average number of residues in the molecule of the polyester may vary from about three to about one hundred twenty.

The reaction is carried out at a temperature high enough and for a time long enough to secure the desired consistency. An elevated temperature preferably is employed to expedite the reaction, but during the preparation of the polyester, the temperature should not be so high nor the time of reaction so long as to cause substantial polymerization. There is less danger of premature polymerization it an inhibiting agent is added before the esterification is carried out.

Whenever added, an inhibiting agent is used in the proportion required to give the desired degree of inhibiting effect. In may be necessary to use different inhibitors in widely ditlerent proportions in order to secure the same inhibiting efi'ect.

Any desired inhibitor such as hydroquinone, pyrogallol, tannic acid or any aromatic amine, such as aniline or phenylene diamine may be employed as an inhibitor.

The preparation of the unsaturated polyester preferably is carried out in an atmosphere of an inert gas such as carbon dioxide, nitrogen or the like, in order to prevent darkening or to make it possible to obtain a pale or colorless product. Bubbling the inert gas through the reacting ingredients is advantageous in that the gas serves the added functions of agitation and of expediting the removal of water formed by the reaction. Exclusion of oxygen is desirable not only because it causes discoloration, but also because it tends to produce premature polymerization at the elevated temperatures used.

The acid number of the product depends upon the degree of reaction and the proportions of acid and alcohol used for the reaction. With equimolecular proportions of dibasic acid and dihydric alcohol, the reaction may be carried to an acid number of about 20. The use of an acid catalyst may make it possible to attain a lower acid number without substantial polymerization. Modifications are numerous and include modification of the unsaturated polyester with saturated alkyd-type resins, oil-modified. alkyd resins, etc. Modification is contemplated also with a minor amount of one or more liquid, ethylenically unsaturated monomeric materials compatible and copolymerizable with said polyester, e.g., styrene, divinyl benzene, vinyl toluene and other nuclearly-substituted styrenes; diallyl esters such as diallyl phthalate, diallyl succinate, diallyl maleate, diallyl itaconite, etc; and other unsaturated esters such as divinyl maieate, dioctyl itaconate, dibenzyl itaconate and the like. Since the art of preparing such curable polymerizable materials and their compositions is Well known (as shown by US. Patents Nos. 2,420,740, 2,453,665, 2,593,787, 2,409,- 633, 2,443,735-2,443,74l, 2,450,552, 2,255,313, 2,512,410, 2,280,256, 2,453,666, 2,510,168, 2,635,089, 2,645,626 and US. applications Ser. No. 307,703, filed Sept. 3, 1952, and Ser. No. 377,265, filed Aug. 28, 1953, now Patent No. 2,777,829), no extended discussion seems necessary here except to point out that many of the polyester-monorncr compositions (which me polymerizable) tend to polymerize more or less rapidly at room temperature, and hence are conventionally stabilized with various polymerization inhibitors. The inclusion of such inhibitors in effective amounts renders the liquid materials stable against polymerization for various periods of time, thereby enabling them to be manufactured and then stored until such time as they are to be used in our coatings. At such time, it has heretofore been conventional practice to add relatively small amounts of curing cata lysts, e.g., enzoyl peroxide. After such catalysts have been added, the compositions tend to polymerize fairly rapidly at room temperature, and faster at higher tem peratures, until they have attained a stable, cured, resinous state.

in general, polyester masses of the types herein described and illustrated above are 100% polymerizable and may frequently be mixtures of two or more unsaturated polyester types or formulations with or Without polymerizable ethylenically-unsaturated monomeric material. Nevertheless, a single polyester type or formulation can be used by itself, just as Well. It is more common, though, to mix two or more diiierent ones together bility and/or rigidity of the cured resin.

since in this way a few stock resin types or formulations can be maintained and from them a large number of blends can readily be prepared. The stock formulations are commonly distinguished from each other on the basis of the rigidity or flexibility of the resins they yield. Thus, one might give flexible resin, another might give a semirigid resin, and a third might give a rigid resin, and their various blends give cured resinous coatings of various degrees of rigidity, selected for the type of service for which the finished product is intended. Those skilled in the art of formulating unsaturated polyester resins recognize that the proportions of saturated oarboxylic acids to cap-unsaturated carboxylic acids, the length of the carbon chain(s) involved in the carboxylic acids and in the polyhydric alcohols, the proportion of polyester t-o polymerizable unsaturated monomer (if any), the type of ethylenic monomer, the degree of functionality in the carboxylic acids and polyhydric alcohols, and the curing treatment(s), are all factors affecting the flexi- Since such knowledge is now known and has been long used by those skilled in the art, and is only an incidental feature in the present invention, no extended discussion of such formulation details seems necessary to enable a person skilled in the art to practice the present invention.

It will be understood by those skilled in the art that most unsaturated polyester components of our coatings, as described above, cannot be fully cured to a hard resinous state in the presence of oxygen; that is, the cure is inhibited by oxygen of the air. This does not means to say that in a thick layer, such as is contemplated here (up to 4 inch or more) the resin cannot be cured at all. On the contrary, it is well known that the inhibiting effect of the air affects only the exposed surface portions and portions immediately thereunder to a depth of a few thousandths of an inch. The remainder of the layer is uninhibited and can be cured fully. The inhibited surface portion is partially cured, but generally remains somewhat soft or even slightly tacky. Such undercured surface is no impediment to the use in this invention of the air-inhibited resins, since in normal use the soft undercured surface portion is soon worn away to expose the harder fully cured portions underneath. There are known ways, however, to prevent the curing-inhibition of air.

One way is to cover the applied layer with films of cellophane or similar material thereby to prevent contact of the air with the surface of the layer being cured.

Another Way is to use hydroxy ether components of the allyl ether type in the preparation of the unsaturated polyester. This expedient is described in US. application Ser. No. 307,703 (now abandoned) and is claimed in the copending continuation-impart application Ser. No. 526,776, filed August 5, 1955, now US. Patent No. 2,852,- 487. When being prepared, the unsaturated polyester formulation includes at least one hydroxy ether which has up to two alcoholic hydroxyls available for esterification and which has the structure obtainable by partial etherification of an aliphatic polyhydric alcohol having up to 6 hydroxyls with an m d-unsaturated aliphatic monohydric alcohol (a) which contains from 3 to 6 carbons, (b) in which the double bond involves the carbon atoms which are in the alpha and beta positions relative to the carbon atom carrying the alcoholic hydroxyl group, and (c) in which said beta carbon atom is a constituent of a terminal methylene group, said hydroxy ether being present in an amount sufiicient to provide at least one a e-unsaturated monohydric alcohol radical per 50 original double bonds provided by said o enedioyl groups in said vehicle and not more than about 2 of said alcohol radicals per each of said original A -enedioyl groups.

A third way is to incorporate in the 100% polymerizable polyester mass a small amount of paraffin wax. The

use of this and other waxy materials is taught in the Parkyn, Boder British Patent No. 713,332. A fourth able, e.g., bentonite.

and somewhat analogous way is to incorporate small amounts of stearic acid. This expedient is described and claimed in the copending US. application Serial No. 670,878, filed July 10, 1957, now abandoned.

Thus, it will be clear that where one desires to avoid the soft, air-inhibited surface portion on the cured layers of our coatings, that can be done by using one of the foregoing expedients, or other known expedients which are less practical.

Importing Hold-Out Fraprrties to the Unsaturated Polyester Component it will be understood from what has been said here inabove that if the polymerizable polyester component were not modified to impart hold-out, it would tend to sink into a porous substrate before it has been cured, and hence would be lost so far as forming a surface layer is concerned. We encountered this difiiculty in an early effort to renew a box car floor. The coating, While being applied, appeared to form a surface layer, but when the floor was inspected about 24 hours later, practically all of the applied coating material had disappeared in to the porous, splintered wood of the original lioor. While it became cured after so sinking in, and thereby greatly strengthened and reinforced the wood, it had not served its intended purpose of giving a new treadable surface layer. In seeking to correct this situation we discovered that such penetration. into a porous substrate could be overcome by incorporating certain finely-divided inorganic solids which modify the rheological characteristics of the polyester mass toward the characteristics of thixotropy. One such material is short fiber asbestos of fine standard plastic filler grade. Another material is pulverized dehydrated silica gel in an uncompressed state. Commercial products of this type are presently available, such as Cabosil (Godfrey L. Cabot Co.), PD-244 Silica (Davison Chemical Co.) or Santocel (Monsanto Chemical Co.). Certain natural and/or treated clays which include combined water in their structure (so-called hydrous clays) are also suit- We prefer asbestos or silica gel, and of the available silica gels we especially prefer those having an apparent density of 4-20 pounds per cubic foot and an effective surface area of about 100-400 square meters per gram.

The asbestos shorts, silica gel and hydrous clays are employed in small amounts usually between about 0.5% and 10% by weight, Different amounts of each are needed, when used individually, to develop optimum holdout. Where mixtures are used, one must usually experiment to determine the optimum amount for each of the different mixtures since the effects do not appear to be directly additive. It will be noted that each of the three classes of materials is of hydrous nature, having small amounts of water combined chemically into its make-up, and we believe that it is the hydrous quality of each and the great surface area presented that aids in developing the presently-desired rheological properties. The silica gels represented by Cabosil, Santocel and PD-244 Silica are dry free-flowing powdery products which still contain small amounts of combined water in their gel structure and are submicroscopic particles having an SiO content (dry basis) of 99.099.7%, 21 free moisture content of 02-20% at C. and a negligible content of C30, MgO and Fe O (see U.S. Patents 2,249,767, 2,535,063, 2,631,082 and 2,625,492, whose teachings are here incorporated by reference). Opaline hydrous siliceous minerals such as hyalite and diatomite are natural products comparable to the above manufactured products which in comminuted form can also be used if low in iron oxides. They can be acid washed to lower the iron content.

Reinforcing the lldodified Polyester After the desired rheological properties have been attained as described under the preceding heading, finelycorneas divided solid materials of a hard abrasive nature are added to impart reinforcement and particularly skidproofness. Thus pulverized sand, pumice, aluminum carbides, aluminum silicides, garnet, glass, porcelain, blastfurnace slag, etc., represents comminuted abrasive materials which can be used. We especially prefer pumice but this preference need not restrain one from practicing the invention with one or more of the other abrasive materials identifid above. The pumice (or other abrasive powder) is added to the rheologically modified polyester mass in relatively large but uncritical amounts. Such amounts can range from about to 50% by weight on the unsaturated polyester.

Color pigments and conventional fillers and extenders such as talc, mica, asbestine, sawdust, papermakers clays, limestone (or other forms of calcium carbonate) can also be included to extend the polyester mass, and Where such materials possess a desired color, they impart usefill color qualities. Most conventional pigments can be used for color and/ or hiding but a few tend to impede cure of the polyesters. To avoid this disadvantage, the pigments and/or fillers should be free of or contain only small amounts of reactive metals such as iron, lead or zinc or their compounds.

APPLICATION OF THE COATING As will be understood, the unsaturated polyesters in general tend to cure rapidly even at room temperature once the curing catalyst is added, and in many cases undergo slow curing reactions even without added catalyst unless already inhibited by additions of known gelling inhibitors. By using such inhibitors, however, the coatings can be prepared so as to be stable against gellation for prolonged periods of time. In the usual practice of this invention, inhibitors would be added for this purpose. When one then is ready to apply the coatings, he can either add a carefully measured quantity of peroxide or other known type of curing catalyst, or he can use a twonozzle spray gun of the type in which the catalyst is sprayed through one nozzle simultaneously with the spraying of the coating material through the other nozzle. A single-nozzle spray gun can also be used in accordance with the principles described and claimed in copendin'g U.S. application Serial No. 349,620, filed March 5, 1953, now US. Patent No. 2,823,143, wherein the catalyst is conveyed to the polyester composition in the air-stream used to atornize the polyester at the single nozzle of the gun. Some of the coatings are apt to be too heavy for spraying through the nozzles of conventional single or double nozzle guns, and where such is the case, the catalyzed coating can be sprayed by using an undcrcoatingtype of spray gun. When spray application is not desired, other methods can be used to apply the alreadycatalyzed material, such as brushing, rolling or spreading with a squeegee or trowel. Application of a batch of already-catalyzed coating should, of course, be completed within the pot life of the catalyzed material, and to this end the size of the batch which is catalyzed should be kept small enough to permit it all to be applied by whatever application method is chosen.

The rheological characteristics of the coating, as secured in the manner described hereinabove, in addition to imparting hold-out of the applied layer and preventing settling in the can, also serve to overcome sagging tendencies when the coatings are applied to vertical surfaces. It is therefore entirely feasible to spray, brush, roll, squeegee or trowel rather thick layers of the coatings to wall surfaces.

The thickness of the applied layer, whether on a horizontal or a vertical surface, can be varied in accordance with ones wishes, as from a few mils in thickness to layers as thick as A or A2 of an inch. For box car floors, layers 40-50 mils thick have been found to be adequate for this type of heavy-duty service. However, where the floors have been badly gouged and are full of pits, splinter cavities, cracks, etc. such depressions can be filled up so as to bring about the formation of a new, level surface. in such instance, some portions of the applied coating may be very thick while the average thickness elsewhere may be around 4il50 mils. For protection of side walls, thicknesses over about 320 mils are seldom apt to be needed, but of course thicker layers can be applied if one so desires.

The applied layers can be cured at ambient atmospheric temperatures above about 65 F. Accordingly, in the case of box cars, the coatings can be applied out-of-doors year round in southern latitudes, and either cut-of-doors or in heated repair shops in the northern latitudes. At 65 F. the coatings require a considerably longer time for curing than at higher temperatures, but in any case it is generally advisable to allow at least 24 hours of curing time before subjecting the applied coating to heavy loads.

It should be understood that our coatings need not be used only for tread surfaces, or for side wall protection', but can be applied to a variety of substrates other than floor or wall surface The coatings need not then include the abrasive solids and can be essentially clear or slightly translucent due to the pigmenting effects of the asbestos, silica gel or clays used to impart rheological modification. Alternatively, such coatings can include pigments to give hiding and/or color, or can be dyed to give clear or translucent layers of desired color. in all such cases, the cured layers afford excellent protective coatings having hardness, toughness, adhesion and chemical resistance and can be subjected to much hard wear, bumping, scraping, etc. without being marred objection ably. If the coatings are to be applied to iron or steel substrates, an amine cured primer composed of an epoxy vehicle and priming pigment (such as red lead and zinc chromate pigment) should be applied in a cured thickness of about 1.5 mils. This primer not only deters rusting but also absorbs some of the differential between the expansion coeilicients of the metal as compared with that of the polyester top coating.

The following examples illustrate the principles of our invention and include the best modes presently known to us for practicing those principles.

Example 1 A coating adapted for use on the floors and side walls of a box car was prepared from the following and other materials: v

A. A liquid polyester of rigid type was preparedtrom Lbs. Propylene glycol 296 Maleic anhydride 169 Phthalic anhydride 254.5 Xylol 57.6 Hydroquinone (Oil-15%) .144 Styrene 282 The first four ingredients were reacted to give a product having an acid number of around 50, after which the xylol was stripped oft in vacuum. The batch was coole somewhat from reaction temperature and the hydroquinone was added and thoroughly mixed in. Then, after further cooling, the styrene was added. The resulting solution had a Gardner-Holdt viscosity of UV at 77 F, a color of 2-3 (Gardner), and an acid number oi 32-36. Weight 9.4 lbs. per gallon.

B. A liquid polyester resin of flexible type was prepared in a similar manner from Lbs.

Diethylene glycol (1.1 mols) 358.7

Maleic anhydride (0.5 mol) 150.7

Adipic acid (6.5 mol) 224.5

Xy-lol 58.7 Acetarnidine 1 hydrochloride solution as stabilizer dissolved in propylene glycol to 20% by weight-.. 2.33

lit eight 9.3 lbs. per gallon.

The foregoing liquid polyesters were employed as the vehicle in the following coating formulation:

Polyester A 6 pints. Polyester B 2 pints.

Silica gel (Cabosil oz. Cobalt naphthenate accelerator 1.81 oz. liq.

51111: density 4 lbs/cu. ft. meters/gram.

2.625 pints cobalt naphthenate dissolved in 5.375 pints styrene; metallic eobalt'content:6%; 7.71 lbs. per gal.

; surface area 200-400 sq.

This coating was catalyzed with 1% Lupersol DDM (methyl ethyl ketone peroxide) and 1% of cobalt naphtheuate, above, and was applied to the door of a box car by means of a squeegee. The coating exhibited excellent hold out, and when cured it produced a tough, translucent coating having good adherence and good durability. It had a tacky surface, however, due to airinhibition of surface cure, and when this surface was worn away, the harder under layer was slippery when wet.

Example 2 To overcome the slipperiness, the formulation of Example l was modified by adding 5 lbs. of pumice, to give a coating having a viscosity of 133 K-U. To overcome the tacky surface, the formulation was further modified by adding 3 liquid ounces of a styrene solution of paraflin wax (refined wax; melting point 123-125" F.) The solution contained 2.5 02s. of wax in 8 pints of styrene;

eight 7.5 lbs. per gallon. When the modified formulation was catalyzed as in Example 1 and applied to a box car floor by squeegee, it yielded a cured layer having sufficient hiding to conceal the underlying Wood. After full curing, the applied coating was tough, hard, skid-proof when wet, and did not crack, chip or separate from the wood when nails were hammered through it and then pulled out by means of a crow bar.

When a coating having the same formulation was applied to the side walls of the box-car by means of a squeegee, it was found that layers up to 20 mils in thickness could be applied without encountering sagging, due to the rheological characteristics imparted by the added silica gel.

Example 3 Results substantially duplicating those of Example 2 were secured when the Ca-bosil Was replaced with 8 oz. of Santocel C. This silica gel had a bulk density of 6 lb-s./ cu. ft. and a particle size of 3-5 microns.

Example 4 Results substantially duplicating those of Example 2 were secured when the 'Cabosil was replaced with 10 oz. Davison Silica Gel PD244. This silica gel had a bulk density of 7.5 lbs/cu. ft. and a surface area of about 290 square meters per gram.

Example 5 Results substantially duplicating those of Example 2 were secured when the Ca-bosil was replaced with 14 oz. of Columbia Southe-rns Hi-Sil 233. This silica gel had a bulk density of 10 lbs/cu. ft., a particle size of .022 micron, and a surface area of 150 square meters per gram.

i0 Example 6 Substantially the same results were secured as in Example 2 by replacing the Cabosil with 10 oz. of short asbestos fiber.

Example 7 Substantially the same results were secured as in Example 2 from the following pigmented formulation which illustrates the use of talc (hydrous magnesium silicate) and silica gel as reheological modifiers.

weight: 15.6 lbs/gal.

- The above formulation exhibits good hold-out when applied to porous wood in its 'as-formulated state. For application to side walls it can be thinned with as much as 1 volume of styrene per 4 volumes of coating for spray application. Even in this diluted state it does not exhibit sagging or running when applied, while still exhibiting excellent hold-out.

Example 8 To overcome air-inhibited under-cured surfaces instead of adding parafiin wax as in Example 2, the formulation of Example 1 can be modified by replacing polyesters A and B with the following polyesters A and B respectively. It will be noted that in these modifications half of the glycol is replaced with an equal molar weight of alpha allyl ether of glycerine (CH :CHCH -O-CH CHOHICH OH) POLYESTER A Lbs. ct-Allyl ether of glycerine 230 Propylene glycol 148 Maleic anhydride 169 Phthalic anhydride 254.5 Xylol, hydroquinone and styrene as in polyester B.

POLYESTER B Lbs. Diethylene glycol 179.4 a-Allyl ether of glycerine 200 Maleic anhydride 150.7 Adipi-c acid 224.5

Xylol, stabilizers, and styrene as in polyester B.

Both modified resins are prepared in the manner described in Example 1.

Example 9 The air-inhibiting effect overcome in Example 2 by adding paraffin wax can be overcome equally well by replacing the Wax with 3 oz. of stearic acid dissolved in the resin.

Example 10 Bentonite was used to replace the Cabosil of Example 2, in an amount of 16 oz. Good hold-out resulted.

While the foregoing examples illustrate air-curing coatings, it should be understood that air-curing characteristics are not indispensable. 1e coatings can be cured equally well, and faster, by heating them as by force drying or baking. Such heating of the coatings does not interfere in any way With preservation of the hold-out qualities which have been exemplified above.

Those skilled in the art will recognize that the principles of this invention can be practiced in a variety of ways and in connection with a multitude of specifically ditierent polyester resin formulations. Such variations in practice are contemplated as'being within the scope of the following claims.

Having described our invention What we claim is:

1. As an article of manufacture, a porous substrate coated with a cured film of the coating composition :hich is a fillable vehicle consisting essentially of a 100% polymerizable liquid mass composed essentially of: (a) an unsaturated polyester resin component Whose molecules contain a plurality of polymeriZably-reactive A -enedioyl groups dissolved in (b) about '7.2%39% by Weight of said polyester component, of liquid copolymerizable and monomeric vinylic hydrocarbon selected from the group consisting of styrene, divinyl benzene, and nuclearly-substituted styrenes, and between about 0.5% and by Weight of said polyester/monomer solution of finelydivided solid hydrous inorganic material selected from the group consisting of dehydrated silica gel having a SiO content of 99.099.7% by Weight on a dry basis, short asbestos fiber, natural opaline minerals, hydrous clays, and mixtures thereof, said hydrous inorganic material being dispersed in said liquid vehicle of polyester/monomer solution and being effective to impart good-hold-out to the coating composition as compared with the same coating from which said inorganic material has been omitted 2. A Wooden article having a surface portion thereof coated with a cured layer of the coating composition defined hereinafter, said article being capable of having nails driven into it through said cured layer and later Withdrawn Without causing cracking, chipping or separation of said layer; said coating composition being a filled vehicle consisting essentially of a 100% polynierizable liquid mass composed essentially of: (a) an unsaturated polyester resin component whose molecules contain a plurality of polymerizably-reactive n -enedioyl groups dissolved in (b) about 7.2%-39% by Weight of said polyester component, of styrene, (a) between about 0.5% and 10% by Weight of said polyester/monomer solution of finely-divided solid hydrous inorganic material selected from the group consisting of dehydrated silica gel having a S10 content of 99.099.7% by weight on a dry basis, short asbestos fiber, natural opaline minerals, hydrous clays, and mixtures thereof, said hydrous inorganic material being dispersed in said liquid vehicle of polyester/monomer solution and being effective to impart good hold-out to the coating composition as compared with the sane coating from which said inorganic material has been emitted, and (d) a tiller component composed of finely-divided, hard, inorganic, inert abrasive material, said filler component corresponding in amount from about 10% to by weight on said liquid vehicle, and being dispersed in said vehicle.

3, A Wooden article as claimed in claim 2 wherein the hydrous inorganic material of the coating composition is a silica gel having an apparent density oi 4-20 pounds per cubic foot, and an eiiective area between about and 400 square meters per gram.

4. A wooden article as claimed in claim 2 wherein the hydrous inorganic material of the coating composition is short asbestos fiber.

References @ited in the file or this patent UNITED ST TES PATENTS 

1. AS AN ARTICLE OF MANUFACTURE, A POROUS SUBSTRATE COATED WITH A CURED FILM OF THE COATING COMPOSITION WHICH IS A FILLABLE VEHICLE CONSISTING ESSENTIALLY OF A 100% POLYMERIZABLE LIQUID MASS COMPOSED ESSENTIALLY OF: (A) AN UNSATURATED POLYESTER RESIN COMPONENT WHOSE MOLECULES CONTAIN A PLURALITY OF POLYMERIZABLE-REACTIVE $2,3-ENEDIOYL GROUPS DISSOLVED IN (B) ABOUT 7.2%-39% BY WEIGHT OF SAID POLYESTER COMPONENT, OF LIQUID COPOLYMERIZABLE AND MONOMERIC VINYLIC HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF STYRENE, DIVINYL BENZENE, AND NUCLEARLY-SUBSTITUTED STYRENES, AND (C) BETWEEN ABOUT 0.5% AND 10% BY WEIGHT OF SAID POLYESTER/MONOMER SOLUTION OF FINELY-DIVIDED SOLID HYDROUS INORGANIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF DEHYDRATED SILICA GEL HAVING A SIO2 CONTENT OF 99.0-99.7% BY WEIGHT ON A DRY BASIS, SHORT ABSESTOS FIBER, NATURAL OPALINE MINERALS, HYDROUS CLAYS, AND MIXTURES THEREOF, SAID HYDROUS INORGANIC MATERIAL BEING DISPERSED IN SAID LIQUID VEHICLE OF POLYESTER/MONOMER SOLUTION AND BEING EFFECTIVE TO IMPART GOOD-HOLD-OUT TO THE COATING COMPOSITION AS COMPARED WITH THE SAME COATING FROM WHICH SAID INORGANIC MATERIAL HAS BEEN OMITTED. 